/**
 * @file
 * SLIP Interface
 *
 */

/*
 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This file is built upon the file: src/arch/rtxc/netif/sioslip.c
 *
 * Author: Magnus Ivarsson <magnus.ivarsson(at)volvo.com>
 */

/*
 * This is an arch independent SLIP netif. The specific serial hooks must be
 * provided by another file. They are sio_open, sio_read/sio_tryread and sio_send
 */

#include "netif/slipif.h"
#include "lwip/opt.h"

#if LWIP_HAVE_SLIPIF

#include "lwip/def.h"
#include "lwip/pbuf.h"
#include "lwip/sys.h"
#include "lwip/stats.h"
#include "lwip/snmp.h"
#include "lwip/sio.h"

#define SLIP_BLOCK     1
#define SLIP_DONTBLOCK 0

#define SLIP_END     0300 /* 0xC0 */
#define SLIP_ESC     0333 /* 0xDB */
#define SLIP_ESC_END 0334 /* 0xDC */
#define SLIP_ESC_ESC 0335 /* 0xDD */

#define SLIP_MAX_SIZE 1500

enum slipif_recv_state {
	SLIP_RECV_NORMAL,
	SLIP_RECV_ESCAPE,
};

struct slipif_priv {
	sio_fd_t sd;
	/* q is the whole pbuf chain for a packet, p is the current pbuf in the chain */
	struct pbuf* p, *q;
	enum slipif_recv_state state;
	u16_t i, recved;
};

/**
 * Send a pbuf doing the necessary SLIP encapsulation
 *
 * Uses the serial layer's sio_send()
 *
 * @param netif the lwip network interface structure for this slipif
 * @param p the pbuf chaing packet to send
 * @param ipaddr the ip address to send the packet to (not used for slipif)
 * @return always returns ERR_OK since the serial layer does not provide return values
 */
err_t
slipif_output(struct netif* netif, struct pbuf* p, struct ip_addr* ipaddr)
{
	struct slipif_priv* priv;
	struct pbuf* q;
	u16_t i;
	u8_t c;

	LWIP_ASSERT("netif != NULL", (netif != NULL));
	LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));
	LWIP_ASSERT("p != NULL", (p != NULL));

	LWIP_UNUSED_ARG(ipaddr);

	priv = netif->state;

	/* Send pbuf out on the serial I/O device. */
	sio_send(SLIP_END, priv->sd);

	for(q = p; q != NULL; q = q->next) {
		for(i = 0; i < q->len; i++) {
			c = ((u8_t*)q->payload)[i];

			switch(c) {
				case SLIP_END:
					sio_send(SLIP_ESC, priv->sd);
					sio_send(SLIP_ESC_END, priv->sd);
					break;

				case SLIP_ESC:
					sio_send(SLIP_ESC, priv->sd);
					sio_send(SLIP_ESC_ESC, priv->sd);
					break;

				default:
					sio_send(c, priv->sd);
					break;
			}
		}
	}

	sio_send(SLIP_END, priv->sd);
	return ERR_OK;
}

/**
 * Static function for easy use of blockig or non-blocking
 * sio_read
 *
 * @param fd serial device handle
 * @param data pointer to data buffer for receiving
 * @param len maximum length (in bytes) of data to receive
 * @param block if 1, call sio_read; if 0, call sio_tryread
 * @return return value of sio_read of sio_tryread
 */
static u32_t
slip_sio_read(sio_fd_t fd, u8_t* data, u32_t len, u8_t block)
{
	if(block) {
		return sio_read(fd, data, len);
	} else {
		return sio_tryread(fd, data, len);
	}
}

/**
 * Handle the incoming SLIP stream character by character
 *
 * Poll the serial layer by calling sio_read() or sio_tryread().
 *
 * @param netif the lwip network interface structure for this slipif
 * @param block if 1, block until data is received; if 0, return when all data
 *        from the buffer is received (multiple calls to this function will
 *        return a complete packet, NULL is returned before - used for polling)
 * @return The IP packet when SLIP_END is received
 */
static struct pbuf*
slipif_input(struct netif* netif, u8_t block)
{
	struct slipif_priv* priv;
	u8_t c;
	struct pbuf* t;

	LWIP_ASSERT("netif != NULL", (netif != NULL));
	LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));

	priv = netif->state;

	while(slip_sio_read(priv->sd, &c, 1, block) > 0) {
		switch(priv->state) {
			case SLIP_RECV_NORMAL:
				switch(c) {
					case SLIP_END:
						if(priv->recved > 0) {
							/* Received whole packet. */
							/* Trim the pbuf to the size of the received packet. */
							pbuf_realloc(priv->q, priv->recved);

							LINK_STATS_INC(link.recv);

							LWIP_DEBUGF(SLIP_DEBUG, ("slipif: Got packet\n"));
							t = priv->q;
							priv->p = priv->q = NULL;
							priv->i = priv->recved = 0;
							return t;
						}

						continue;

					case SLIP_ESC:
						priv->state = SLIP_RECV_ESCAPE;
						continue;
				}

				break;

			case SLIP_RECV_ESCAPE:
				switch(c) {
					case SLIP_ESC_END:
						c = SLIP_END;
						break;

					case SLIP_ESC_ESC:
						c = SLIP_ESC;
						break;
				}

				priv->state = SLIP_RECV_NORMAL;
				/* FALLTHROUGH */
		}

		/* byte received, packet not yet completely received */
		if(priv->p == NULL) {
			/* allocate a new pbuf */
			LWIP_DEBUGF(SLIP_DEBUG, ("slipif_input: alloc\n"));
			priv->p = pbuf_alloc(PBUF_LINK, (PBUF_POOL_BUFSIZE - PBUF_LINK_HLEN), PBUF_POOL);

			if(priv->p == NULL) {
				LINK_STATS_INC(link.drop);
				LWIP_DEBUGF(SLIP_DEBUG, ("slipif_input: no new pbuf! (DROP)\n"));
				/* don't process any further since we got no pbuf to receive to */
				break;
			}

			if(priv->q != NULL) {
				/* 'chain' the pbuf to the existing chain */
				pbuf_cat(priv->q, priv->p);
			} else {
				/* p is the first pbuf in the chain */
				priv->q = priv->p;
			}
		}

		/* this automatically drops bytes if > SLIP_MAX_SIZE */
		if((priv->p != NULL) && (priv->recved <= SLIP_MAX_SIZE)) {
			((u8_t*)priv->p->payload)[priv->i] = c;
			priv->recved++;
			priv->i++;

			if(priv->i >= priv->p->len) {
				/* on to the next pbuf */
				priv->i = 0;

				if(priv->p->next != NULL && priv->p->next->len > 0) {
					/* p is a chain, on to the next in the chain */
					priv->p = priv->p->next;
				} else {
					/* p is a single pbuf, set it to NULL so next time a new
					 * pbuf is allocated */
					priv->p = NULL;
				}
			}
		}
	}

	return NULL;
}

#if !NO_SYS
/**
 * The SLIP input thread.
 *
 * Feed the IP layer with incoming packets
 *
 * @param nf the lwip network interface structure for this slipif
 */
static void
slipif_loop_thread(void* nf)
{
	struct pbuf* p;
	struct netif* netif = (struct netif*)nf;

	while(1) {
		p = slipif_input(netif, SLIP_BLOCK);

		if(p != NULL) {
			if(netif->input(p, netif) != ERR_OK) {
				pbuf_free(p);
				p = NULL;
			}
		}
	}
}
#endif /* !NO_SYS */

/**
 * SLIP netif initialization
 *
 * Call the arch specific sio_open and remember
 * the opened device in the state field of the netif.
 *
 * @param netif the lwip network interface structure for this slipif
 * @return ERR_OK if serial line could be opened,
 *         ERR_MEM if no memory could be allocated,
 *         ERR_IF is serial line couldn't be opened
 *
 * @note netif->num must contain the number of the serial port to open
 *       (0 by default)
 */
err_t
slipif_init(struct netif* netif)
{
	struct slipif_priv* priv;

	LWIP_DEBUGF(SLIP_DEBUG, ("slipif_init: netif->num=%"U16_F"\n", (u16_t)netif->num));

	/* Allocate private data */
	priv = mem_malloc(sizeof(struct slipif_priv));

	if(!priv) {
		return ERR_MEM;
	}

	netif->name[0] = 's';
	netif->name[1] = 'l';
	netif->output = slipif_output;
	netif->mtu = SLIP_MAX_SIZE;
	netif->flags |= NETIF_FLAG_POINTTOPOINT;

	/* Try to open the serial port (netif->num contains the port number). */
	priv->sd = sio_open(netif->num);

	if(!priv->sd) {
		/* Opening the serial port failed. */
		mem_free(priv);
		return ERR_IF;
	}

	/* Initialize private data */
	priv->p = NULL;
	priv->q = NULL;
	priv->state = SLIP_RECV_NORMAL;
	priv->i = 0;
	priv->recved = 0;

	netif->state = priv;

	/* initialize the snmp variables and counters inside the struct netif
	 * ifSpeed: no assumption can be made without knowing more about the
	 * serial line!
	 */
	NETIF_INIT_SNMP(netif, snmp_ifType_slip, 0);

	/* Create a thread to poll the serial line. */
	sys_thread_new(SLIPIF_THREAD_NAME, slipif_loop_thread, netif,
	               SLIPIF_THREAD_STACKSIZE, SLIPIF_THREAD_PRIO);
	return ERR_OK;
}

/**
 * Polls the serial device and feeds the IP layer with incoming packets.
 *
 * @param netif The lwip network interface structure for this slipif
 */
void
slipif_poll(struct netif* netif)
{
	struct pbuf* p;
	struct slipif_priv* priv;

	LWIP_ASSERT("netif != NULL", (netif != NULL));
	LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));

	priv = netif->state;

	while((p = slipif_input(netif, SLIP_DONTBLOCK)) != NULL) {
		if(netif->input(p, netif) != ERR_OK) {
			pbuf_free(p);
		}
	}
}

#endif /* LWIP_HAVE_SLIPIF */
